Universal waste processor

ABSTRACT

A unique waste processing method provides a simple solution to complex mix of waste streams using a molten sodium/potassium bath to thermalize waste. The process offers sterilization, volumetric reduction, energy or oil recovery, and complete molecular fragmentation of hazardous chemicals.

CROSS-REFERENCE TO RELATED APPPLICATION

This application claims the benefit of Provisional application Ser. No.60/724,097, filed Oct. 6, 2005.

FEDERALLY SPONSERED RESEARCH

Not Applicable

SEQUENCE LISTING OR PROGRAM

Not Applicable

BACKGROUND

The present invention relates to an apparatus and method forthermolizing industrial, residential, and medical waste for the purposesof sterilization, energy or oil recovery, molecular decomposition, andvolumetric reduction of waste.

While there are alternative systems to process waste throughincineration, autoclaving and gasification, they pale in comparison withregards to making the waste safe for disposal. In waste processing, ifthe process does not provide complete molecular decomposition into basicelements, it is incomplete, unsafe and does not meet the needs of thetwenty-first century.

One would have to conclude that if the condensed steam from autoclavingmedical waste contains mercury so does the processed waste. And yet,with the existing laws, autoclaved medical waste is shredded and takento municipal landfills to leak its dangerous chemical contents such asmercury into the groundwater. In fact, traces of chemo and heartmedication has now found its way into our lakes and rivers.

Furthermore, natural decaying, as in backyard composts, septic tanks, ormunicipal landfills, are also not a viable options because they areextremely slow and produce heat, VOC's, CO, CO₂ same as incompletecombustion even though the process is seemingly safe and anaerobic. Innatural decaying the oxygen is supplied from atmospheric moisture andgroundwater.

On the other hand, burning waste as in incineration, forms and releasestoxic chemical compounds into the air and spreads the contamination overa wider area. There are also so many variations of incineration underthe heading of pyrolysis. It seems any combustion system with controlledoxidation is mistakenly classified under the heading of “pyrolysis.”Thus the term “thermolysis” is used herein to differentiate this processfrom pyrolysis.

Used tires also present a unique disposal problem due to their bulkyshape and size. While shredding improves the disposal problem, it is anexpensive alternative and does not recover any of the renewableresources from the used tire.

Many prior attempts to recycle tires through pyrolysis have not provensuccessful. In dealing with tires, mere carbonization is not the primaryissue, but the efficiency and maximizing oil production is. Ability tomaintain process temperature with accuracy is also an essentialcomponent in the producing good quality oil. Furthermore, tires do notlend themselves to pyrolysis by hot metal contact due to their size andshape. Only a small portion of the tire can be contacted with the hotmetal, therefore processed.

While high temperature steam systems are better suited for handling theshape and size but necessitate high-pressure vessels to handle thetemperatures and pressures involved, making the system unnecessarilydangerous, inefficient and expensive. Microwave technology has alsoproven unsuccessful for this application.

Prior art by the same inventor (application Ser. No. 10,217,386 Art Unit1764) depicts an apparatus and method most suitable for processing bulkmedical waste, but not suitable for intact tires. Furthermore, theoptimum operating temperature of the inferenced apparatus being 1500° F.is too high for optimum oil production. Higher temperature is moresuited for vaporizing into gaseous product with higher molecularfragmentation. The optimum processing temperature for oil productionfrom used tires is 1216° F.

SUMMARY OF INVENTION

Two distinct systems are provided for thermolizing: a batch unit, whichprocesses a batch of waste at a time, and a continuous system requiringcontinuous feed to support a continuous thermolysis process. Bothsystems however utilize the same concept of controlled incrementalimmersion of waste into a molten salt bath solution and a secondarymeans of superheating of gasses for complete molecular decomposition.Both systems also utilize a sealed containment for collecting, treatingand partially or fully oxidizing the vaporized gasses to maintainprocess temperature.

The continuous system consists of a liquid salt bath configured within asealed containment with interlocked double sealed entry gates, internalconveyors and heating system. The benefit of using liquid salt for heattransfer is that it lowers the required process temperature whileaffording fast process time. Furthermore, the set point processtemperature can be maintained more precisely owing to the high heatcontent of sodium/potassium solution, making the medium behave more likea heat storage.

In both cases, a salt bath is utilized which is preheated by means ofelectrical resistance, propane or natural gas. The switch over tomanufactured gas is automatic, based on the amount of manufactured gasavailable. Since neither the quantity (CFM) nor the quality (Btu/CF) ofthe manufactured gas is known with any certainty, the combustionstoichiometry is maintained by controlling the combustion air to matchthe manufactured gas available by means of monitoring the O₂ in theexhaust stream.

The process temperature is controlled independently by means ofcontrolling the BTU/SF content by adding propane or natural gas to themanufactured gas to increase the process temperature or by pumping wasterinse water through a tube inside the salt bath to lower the processtemperature. If excess heat is a constant as in medical waste, this canbe harnessed for other uses. Best way to accomplish this is to circulatethe liquid salt through a heat exchanger.

The continuous system utilizes a conveyor with protruding spikes ortreads to engage with tires or waste for the purposes of regulating theimmersion speed of the waste into the salt bath. The intent of P.I.D.(proportional integral derivative) controlled immersion is to producesteady controllable vaporization pressure within the sealed chamber. Thestoichiometry of the combustion air to fuel ratio is regulated by abutterfly valve slaved to the exhaust O₂ sensor. As usual standardpractice 10% excess air is used for the cleanest combustion. This tendsto provide a hot flame temperature suitable for molecular fragmentationwithin the heat exchanger.

The remaining residue consists of metals and carbon black. Carbon beinglighter than liquid sodium floats on the surface. The discharge conveyorcollects and discharges all solids floating carbon and metallic partsinto the rinse tank.

The batch system uses a wire basket with a lid to contain and immersethe waste incrementally into the salt solution. A quick water rinsecycle follows the thermolyzation cycle to wash off and collect any saltremaining on metallic parts within the basket. Depending on the meshsize of the wire basket, the carbon may be collected within the basketor by the screen over the rinse water holding tank. The rinse water fromthe holding tank is then used in the next cycle to cool the processtemperature or to maintain the steam-laden atmosphere necessary for theprocess.

Sodium/potassium solution also facilitates the capturing andneutralizing of hydrochloric acids released during thermolysis ofchlorinated plastics. Sodium carbonate is added as additive tocompensate for losses.

While thermolysis is best achieved by subjecting the waste to high heatin an anaerobic, steam-laden environment, total fragmentation is notdesirable when dealing with used tires. So, the process temperature iscase specific depending on the type of waste and level of molecularfragmentation desired. With tires, if oil is the desired byproduct theinitial process temperature should not exceed 1216° F.

Five years of test data however shows that, regardless of the setprocess temperature, the initial step of the vaporization never produces100% decomposition. This is because the very nature of vaporization fromsolid or liquid to gaseous product requires high thermal energy causinga local cooling effect thus, impeding the decomposition of fragmentationprocess. The vaporized gasses, also insulate the waste from the heatsource during vaporization, further impeding the process. This is why athree-step process is utilized in this apparatus, first step is tovaporize the waste, the second step is to distill in the case of tiresor filter by adsorption in the case of medical waste, and a third todefragment molecules by higher heat just before the gasses are oxidized.

Thermolysis however, does not treat nor break down heavy metals. This isbecause heavy metals like mercury, and lead are already naturalelements. In this case, if required, adsorbers are used to capture theheavy metals into activated charcoal and lignite in-line filter.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 depicts a continuous system. The powered conveyor (11) conveysthe solid waste (12) into the sealed loading chamber vestibule (35). Theinterlocked gates (13) at either end of the vestibule openindependently, one at a time, to maintain the integrity of the anaerobicatmosphere within the salt bath chamber (36). The spiked charge conveyor(18) engages with the solid waste for controlled immersion into the saltbath (14). Discharge conveyor (17) collects all residue from the saltbath and discharges into the rinse tank (20) for final disposal by asecond discharge conveyor (17). The salt bath is insulated to minimizeheat loss.

FIG. 2 depicts a batch system. The apparatus consists of a sealedcontainment (101) with gas tight sealed gate (102) and an insulated saltbath (103). The waste-processing basket (109) is supported by twoarticulating arms, to allow the basket to traverse from thermolizingposition, through rinse cycle in the upright position to load/unloadposition outside the front gate. The movement of the articulating arm iscontrolled by a PLC (programmable logic controller). An in-linecarbon/lignite absorber (111) is added for waste streams containingheavy metals. The scrubbed gas is directed through piping (110) to thesuper-heater (114) for complete molecular fragmentation before oxidationin burners (125).

DETAILED DESCRIPTION OF DRAWINGS

FIG. 1 depicts a continuous system where, the powered conveyor (11)conveys the solid waste or tire into the sealed loading chambervestibule (35). The interlocked gates (13) at either end of thevestibule open independently, one at a time, to maintain the integrityof the anaerobic chamber (14). The salt bath is equipped with a coolingtube (15). Evaporation of water inside the tube provides the cooling ofprocess temperature.

Two independent conveyors are fitted within the anaerobic chamber (14).The charge conveyor (18) is designed to engage with the waste usingspikes (30) attached to the conveyor belt to control the immersion rateof vaporization. The discharge conveyor (17) is designed to capture andremove byproducts, namely carbon black (21) and wires and metallic parts(31) from the salt bath. The fire tube (19) is submerged and extendsacross the salt bath and back with sufficient diameter to accommodatethe flame and length to transfer the heat from the combustion to themolten salt.

The discharge from the byproduct conveyor (17) is gravity fed into thewater rinse bath (20), which also acts as a seal against manufacturedgasses escaping from the sealed containment (14). Surface of the rinsebath water exposed to the hot side is minimized to limit the heattransfer into the rinse water.

If desired, the vaporized gasses can be partially condensed andextracted as oil. A condensing coil with a condensate discharge valve isfitted in-line between the anaerobic chamber (14) and the superheater(33) to facilitate the removal of oil. The cooling water (22) for thecondensing coil can be re-circulating through a heat exchanger orevaporative water tower to maintain the water temperature close toambient as possible. The condensing tube (23) is sized to accommodatethe flow rate with sufficient length to condense the oil (29) at nearambient pressure.

The condensate separator (24) is designed to discharge liquid volatilesand or oil including water but capture gasses. It utilizes a float tosense the presence of liquids to open the discharge gate for theliquids. The function of the superheater (25) is to fragment themanufactured synthesis gas through high heat within steam ladenatmosphere to achieve the cleanest possible combustion. The burner (34)premixes the gas with combustion air. The amount of air required isdetermined by the O₂ sensor (26) in the exhaust, which drives the airmixture control valve (28).

Spray mist nozzles (28) directed at the second interlocked entry gate isto (a) lower the gate and bulkhead temperature sufficiently to utilizesilicone or Viton® seals and (b) to maintain positive pressure withinthe vestibule to prevent the backflow of gasses while the inner gate isopen.

FIG. 2 depicts a batch system. The apparatus consists of a sealedcontainment (101) with gas tight sealed gate (102) and an insulated saltbath (103). The waste-processing basket (109) is supported on twointerconnected articulating arms (108), to allow the basket to traversefrom thermolizing position, through the rinse cycle in upright positionto load/unload position outside the front gate (102). The movement ofthe articulating arm is controlled by a PLC (programmable logiccontroller) based on pressure within the anaerobic containment (101).

The burner assembly (125) including the ends of the fire tubes (104) arepositioned outside the sealed containment (101). The number of burnerscan be singular or multiple, depending upon the total Btu requirement.Each burner is equipped with an airflow regulator valve (116), gas flowregulator (115), and an exhaust fan (112) to draw the proper mixture ofnatural gas, manufactured synthesis gas, and air into the heating tubefor true stoichiometric combustion. The amount of air for combustion isregulated by valve slaved to the O₂ sensor (113) located at the exhaustend of the fire tube.

The solenoid valve (123) is activated to spray water through the nozzles(107) when the basket (109) is in the rinse cycle. The salt bath (103)is fitted with an insulated lid (105) to keep the splash from the rinsespray from cooling the molten liquid medium (119).

The vaporized gasses from the containment vessel (101) are directedthrough the pipe (102). An activated charcoal/lignite adsorber (111) isinstalled in line, if the waste to be processed contains heavy metals.The adsorber canister is fitted with a condensate float valve (122) toreturn the condensate from the adsorber canister back to the liquidholding tank (106) via the return line (121). The condensate along withthe waste rinse water is injected by pump (117) through piping (120) andvaporized in the following cycle to generate the steam-laden atmosphere.

The superheater (120) is sized to ensure complete molecularfragmentation before the gasses reach the burner (125). The burner isequipped with a gas flow control valve (115) to blend in natural gas orpropane should the Btu content of the manufactured synthesis gas fallbelow what would be required to maintain process temperature.

1. A batch waste processing apparatus comprising the steps of: (a) Aperforated basket supported on two articulating arms allowing the basketto extend out of the sealed containment for loading bagged or bulkwaste; (b) Means to activate the sequenced action of mechanicallyactuating the arms to traverse the basket inside the sealed containment;(c) Means to seal the door and enable upon locking, the next sequencedevent: to partially submerge the basket into the hot liquidsodium/potassium liquid; (d) Means to control system to automaticallymaintain the correct level of basket submersion into the molten saltbath to maintain a constant predetermined pressure inside the anaerobicchamber equating to a constant gasification rate; (e) Means to causemolecular fragmentation of manufactured gas before oxidizing using ahigh temperature heat exchanger coupled to the fire tube; (f) Means tomatch the correct amount of combustion air to the available fuel bymonitoring the remaining O₂ in the exhaust; (g) Means to monitor andmaintain set process temperature by pumping waste rinse or fresh waterthrough a tube inside the salt bath to lower process temperature orincrementally adding propane or natural gas to the manufactured gas toincrease the process temperature; (h) Means to detect the end of theprocess cycle by the fully submerged basket position; (i) Means toadvance process to the next sequence by moving the basket to the rinseposition; (j) Means to commence rinse cycle activating the rinse watersolenoid and timing the rinse cycle; (k) Means to determine and announcethe end of the cycle and enable opening of the sealed door.
 2. Acontinuous waste processing apparatus comprising the steps of: (a) Aninsulated and sealed containment for molten salt solution; (b) Means forholding process temperature using propane, natural gas or resistanceelectric heaters while idle; (c) Means for holding process temperatureby oxidizing manufactured synthesis gas inside fire tubes whileoperating; (d) Means for vaporizing water in a tube submerged inside thesalt bath to prevent overheating; (e) Means for loading a batch of wastewhile maintaining anaerobic seal within the containment utilizing dualtrap doors; (f) Means for engaging, capturing, and transporting wastethrough the salt bath using a spiked conveyor belt; (g) Means forwashing off metals and carbon black free of salt with rinse water; (h)Means for creating a gas seal with rinse water; (i) Means for separatingcondensate or liquid oils from gasses; (j) Means for further fragmentingthe synthesis gas using combustion heat; (k) Means for controlling thecombustion stoichiometry by controlling combustion air to match thetotal fuel available; (l) Means for adding natural gas or propane tomanufactured gas to ensure minimum process temperature is maintained;(m) Means for controlling immersion rate of waste to match the desiredrate of gasification.
 3. Apparatus of claim 1 or claim 2, where in-linecarbon adsorber can be added to remove heavy metals from the gasifiedwaste.
 4. Apparatus of claim 1 or claim 2, where useful oils or fuel canbe extracted from the vaporized gasses by means of distillation; 5.Apparatus of claim 1 or claim 2, where thermal energy can be recoveredby recirculating exhaust gas, or liquid salt through a heat exchanger.6. Apparatus of claim 1 or claim 2, where hazardous waste is fragmentedinto safe constituent elements through high temperature reheat process.